api/wayland: fix Window not being Send+Sync
api/wayland: fix Window not being Send+Sync

nc4rrillo/glutin,bvssvni/glutin,kornholi/glutin,mmatyas/glutin,vberger/glutin,mbrubeck/glutin,ecoal95/glutin,mitchmindtree/glutin,tomaka/glutin,mbrubeck/glutin,ozkriff/glutin,notriddle/glutin,tomaka/winit,servo/glutin